Recently, there have been used radiographic-imaging methods by using a radiation image conversion panel employing a photostimulable phosphor.
The photostimulable phosphor layer of a radiation image conversion panel for use in these radiographic-imaging methods requires high radiation absorbance and light conversion rate, superior image graininess and enhanced sharpness.
There have been conducted studies of controlling plural factors relating to sensitivity and image quality to achieve improved sensitivity and image quality. Specifically, there has been attempted controlling the shape of the formed photostimulable phosphor as a means for improving sharpness of radiation images, thereby achieving improvements in sensitivity and sharpness.
As one of such attempts is disclosed, for example, in JP-A No. 61-142497 a method of using a photostimulable phosphor layer formed by depositing a photostimulable phosphor on a support having a finely indented surface pattern and comprised of pseudo-columnar blocks (hereinafter, the term JP-A refers to Japanese Patent Application Publication).
Further, there were proposed a method of using a radiation image conversion panel comprised of a photostimulable phosphor layer formed by subjecting cracks between columnar blocks obtained by depositing a photostimulable phosphor on a support having a microscopic pattern to a shock treatment and developing them, as described in JP-A No. 61-142500; a method of using a radiation image conversion panel comprising a photostimulable phosphor layer formed on the surface of a support, in which cracking was caused on the phosphor layer surface to form pseudo-columns, as described in JP-A No. 62-39737; and a method in which a photostimulable phosphor layer having voids was formed by deposition on the surface of a support, followed by being subjected to a heating treatment to grow the voids to form cracks, as described in JP-A No. 62-110200.
There was also proposed a radiation image conversion panel comprising a photostimulable phosphor layer in which spindly columnar crystals were formed through vapor phase deposition on a support (hereinafter, also denoted as a substrate), at a given inclination to the direction normal to the support (as described in, for example, patent document 1).
These attempts of controlling the form of the photostimulable phosphor layer are featured in that formation of a photostimulable phosphor layer comprised of columnar crystals can inhibit diffusion of stimulated light (stimulated emission) in the lateral direction (in which the stimulated light reaches the surface of a support after repeating reflection on the columnar crystal interface).
These radiation image conversion panels comprising a photostimulable phosphor layer formed by vapor phase growth (deposition) achieved an enhanced relationship between sensitivity and sharpness. Further, there was an attempt of combining the phosphor layer comprising columnar photostimulable phosphor crystals with a layer exhibiting a low refractive index, whereby reflection or refraction on the layer surface was inhibited and enhanced image quality was achieved (as described, for example, in patent document 2).
However, a phosphor layer comprised of columnar photostimulable phosphor crystals, in which spindly columnar crystals were formed on the substrate, often resulted in insufficient attachment (adhesiveness) onto the substrate and was easily peeled off, so that improved durability was desired. Specifically, the use of a highly reflective support tended to result in deteriorated adhesion (as described, for example, in patent document 3), so that when physical impact was applied, for instance, when the radiation image conversion panel was dropped, the phosphor layer was peeled off or tendency of causing cracking of the overall layer was marked.
Patent document 1: JP-A No. 2-58000
Patent document 2: JP-A No. 1-131498
Patent document 3: JP-A No. 2004-251883